Generally, an ECD method is used for a Tandem mass spectrometry (MS/MS) in which peptide or protein ions having multiple positive charges are confined in an ion trap, an electron beam is injected into the ion trap, and multiple ionized molecules are coupled with electrons in the ion trap and dissociated. Further, the electrons having low energy are coupled with neutral molecules in an FT-ICR ion trap, thereby forming anions.
A trial operation of a conventional ECD apparatus should be conducted a day ahead in order to operate the apparatus, and thus a high vacuum state having a high vacuum environment of 1×10−7 to 1×10−11 torr should be prepared in the FT-ICR ion trap. Even in the case of an operation of the day, a preheating time of at least about 2 hours is required until a change in pressure due to heat generated in a heating part when generating thermoelectrons is stabilized.
Further, since a high electric current should be applied in order to heat a filament, a lot of power is consumed, and thus it is difficult to precisely control energy and an electric current in the thermoelectrons heated to a high temperature. Further, when the neutral molecules are coupled with the electrons and generate the anions, it is advantageous for the electrons to have lower energy.